Lumbar instability is a common clinical disease, and early changes of lumbar are often caused by the internal structural disorder of the discus intervertebralis or the degenerative discogenic low back pains. With the development of the disease, vertebral bone hyperplasia, vertebral facet joint degeneration, and hypertrophy of ligamentum flavum will occur, which will lead to instability of the spine and spinal stenosis, along with mechanical pain of lumbar and symptom of lumbar spinal stenosis. When the conservative treatments fail, a surgery is often needed. The traditional surgical is fusion surgery, but studies have shown that it is not ideal through long-term clinical follow-up. As the fusion bracing destroys the biomechanical properties of the lumbar segments, the load transmission does not meet the original physiological conditions, thereby resulting in stress concentration and causing retrogression in the adjacent segments of the disc and in the vertebral facet joints.
The “non-fusion bracing” is the development trend of spine surgery in the future. “Non-fusion bracing” refers to a bracing method without fusion, which is implemented through changing the motion orientations and the load of the moveable lumbar segments, and which can control abnormal activities and allow physiological load transmission, thereby alleviating pains and effectively reducing the risks of accelerated degeneration of adjacent segments.
There are many types of non-fusion bracing, and most of the current researches relate to non-fusion interspinous process distractors. For example, the X-stop device described in the patent US20050075634A1 includes an elliptical central axis with a diameter of 10 mm at the middle segment and a length of 10 mm, and protuberant wings arranged at two ends thereof. The outer dimensions of the device are about 34.54×31.24×18.44 mm. The U.S. Pat. No. 6,946,000B2 describes a Wallis device, which comprises a band woven by two pieces of rough polyester and is fixed on a spacer made of Poly (ether ether ketone). The U.S. Pat. No. 5,645,599 describes a Coflex device, which consists of a U-shaped interspinous process spacer and four swings. The U.S. Pat. No. 6,626,944B1 describes a DIAM device, which is dumbbell-shaped and consists of a silicone externally applied polyethylene pipe.
However, in all the surgical methods mentioned in the relevant clinical documents, no matter the X-stop, the WAllis, the Coflex or the DIAM device, it is implanted through an open surgery, the procedure of which is complex and greatly increases the risks and pains of the patient. In addition, some interspinous process braces, such as In-space and Superion, can be implanted by minimally invasive procedures, but the incision is still greater than 2 cm.
Moreover, because its strength is far higher than that of the spinous process, the brace made of metal materials, such as the X-stop device, is likely to cause stress shielding and cause complications such as spinous process rupture.